Despite improvements in modern diesel trucks, in terms of starting ease and drivability during engine warm-up, many diesel truck drivers are still in the habit of leaving their trucks idling unattended for extended periods. This habit apparently stems from prior generations of diesel truck engines that were difficult to restart after being shut down for an extended time period. Thus, the truck may sit idling for a half-a-day or longer while fuel is unnecessarily consumed and the engine and other components experience unnecessary wear. Much of the idling is unnecessary and occurs while the driver has left the truck unattended with the engine idling, often for extended time periods, as when stopping for meals or other breaks.
A typical diesel truck engine may consume 1 to 1.5 gallons of diesel fuel per hour while idling, in comparison to a typical fuel consumption of about 6 to 21 gallons per hour while the truck is operating on the road. Depending on the particular driver, a large portion of the fuel consumed, and the wear on the engine and other related mechanical components, occur during unnecessary idling.
Presently, unnecessary idling of a vehicle engine may be prevented by using an engine idle sensor and a mechanical timer cooperating with the sensor to shut off the engine after the engine has idled for a predetermined time period. For example, U.S. Pat. No. 15,764 (Dec. 2, 1886) to Griffin discloses a gas cutoff valve and spring clock connected to the gas cutoff for stopping an engine after a predetermined time.
Similarly, U.S. Pat. Nos. 1,442,311 and 1,442,312, both to Watson, disclose timers for interrupting the idling of truck engines in particular, to thereby economize the consumption of fuel and to save wear on the engine and other components. These two patents disclose various mechanical approaches to activating a clocktrain which times out and interrupts the ignition circuit after a predetermined idling time. As described in U.S. Pat. No. 1,442,312, before the advent of automatic starters, "unnecessary" idling of an engine was quite common. U.S. Pat. No. 2,580,080 to Dewhirst discloses sensing a lower oil pressure occurring during engine idling to initiate a timer for shutting down the idling engine.
The parking brake may also be used to trigger a timer for shutting down an idling engine after a predetermined time. For example, U.S. Pat. No. 2,031,139 to Ury discloses a device for stopping the idling engine of a truck after a predetermined period wherein a clock timer is activated when the emergency or parking brake is applied. Similarly, U.S. Pat. No. 1,854,868 to Talkes et al. discloses an ignition cutoff using an electric heater, bimetallic strip, and thermostat to perform the timing function, the initiation of the timer being triggered by the emergency brake.
Truck engines in particular are likely to be left unnecessarily idling for an extended period. Accordingly, many modern diesel trucks are equipped with electronic engine control systems that include sensors that may sense idling of the engine. In an attempt to prevent unnecessary idling, the electronic engine controls may also include an engine idle shut-down system that initiates a timer responsive to the driver applying the parking brake. The engine is shut down a predetermined time after the parking brake has been applied.
Unfortunately, many drivers are aware that the engine idle shut-down may be readily bypassed by simply not applying the parking brake. The driver may chock the truck wheels and avoid using the parking brake, or worse, the driver may simply conclude that parking on a level surface is all that is needed to prevent a run-away truck. The parking brake approach to initiate idle shut down may unintentionally serve as a deterrent to safety, by encouraging a driver to avoid using the parking brake. It is also possible that the driver, through inadvertence, may fail to apply the parking brake. Whether the driver intentionally bypasses the idle shut-down or simply forgets to apply the parking brake, the undesirable adverse effects on overall fuel economy and engine wear are the same.